Continued from 1st file…

Igneous Rocks Igneous rocks form from magna. There are two distinct types. Intrusive igneous rocks form before magma reaches the

surface when it slows and crystallizes. Also called plutonic “after Pluto, the god of the lower world” these rocks usually stay below the surface unless enough erosion has occurred to expose them.6

Extrusive Igneous Rocks form when lava hardens at the surface. Also know as volcanic “after the Roman fire god Vulcan” these rocks are more common in “western portions of the Americas.”7

IgneousRhyolite

I believe this rock to be Rhyolite. Part of the Igneous family of rocks. Its texture is

aphanitic or “fine grained” and it is a rosy/gray color.8 Rhyolite

is not as common as other forms of Igneous rock but

occurs in areas where volcanoes are present. I am

probably wrong but this is my best guess.

Igneous Andesite

This rock looks to be andesite. It is “medium-gray, fine-grained” and also contains what look like black crystals.9 Andesite is also commonly found around volcanoes located around the Pacific Ocean so again it makes sense that I would find this near Mt.

Shasta.

IgneousNorite

I had a hard time attempting to name this rock. It looks like a lot of different rocks and the

texture is hardly telling. I think it looks most like

Norite. Norite is a intrusive igneous rock meaning it is

coarse grained and contains minerals which are visible on this rock in

the light.

Sedimentary RocksSedimentary rocks are a collection of sentiment formed

over time through a natural process. Weathering is where it starts. Rocks that already exist

are broken down into sediment. Then the sediment is carried away by “runoff and groundwater.”10

The sediment then slows and settles forming layers. There are different ways that sediment is transported

and formed into “solid rocks” and that is why sedimentary rocks are broken down into three categories; detrital, chemical, and organic.11

SedimentaryConglomerate

This is a really good clear example of conglomerate detrital sedimentary rock because it very obviously contains many other smaller rock particles. I think I found this and a few

others like it at Mount Shasta because of the glacial activity there along with the occurrence of avalanches on the

constantly snow capped mountain.

Metamorphic RocksMetamorphic rocks always have a parent rock that can

come from one of the three categories of rocks. Metamorphic “means to change form” and that is exactly how metamorphic rocks are formed and classified.12 Metamorphism usually happens in 3 ways.

Thermal metamorphism is when a rock changes because of heat.

Hydrothermal metamorphism happens when a rock encounters chemical heat.

Regional metamorphism occurs when rocks “are subjected to the directed pressures and high temperatures associated with large-scale deformation.”13

MetamorphicSchist

To me this rock resembles schist. Schist is a type of metamorphic rock that is

formed over time by “heat, pressure, or stress” and all of those things were surely happening up until the last 200 years on Mt. Shasta.14

Sources1Tarbuck, E. J., & Lutgens, F. K. (2011). Earth: An introduction to physical geology. New Jersey: Pearson Prentice Hall. Pg.

151.

2Mount Shasta Companion. (n.d.). Geology. Retrieved November 28, 2011, from http://www.siskiyous.edu/shasta/geo/his.htm

3Mount Shasta Companion.

4Mount Shasta Companion.

5Mount Shasta Companion.

6Tarbuck, E. J. Pg. 110.

7Tarbuck, E. J. Pg. 110.

8Tarbuck, E. J. Pg. 117.

9Tarbuck, E. J. Pg. 119.

10Tarbuck, E. J. Pg. 201.

11Tarbuck, E. J. Pg. 202.

12Tarbuck, E. J. Pg. 31.

13Tarbuck, E. J. Pg. 31.

14Tarbuck, E. J. Pg. 230.